Assuming it’s Qantas points, you will need to find a oneworld or Qantas partner airline that services Tribhuvan Airport, as Qantas does not fly there. From a very quick search, one reasonable option I could find was Qatar Airways from Kathmandu > Doha > Frankfurt. Best way to search Qatar availability is using BA Executive Club search engine (create an account with a UK address). I have no idea when you want to fly, so don’t know if any seats are available. It would be ~78,000 points in business, or 42,000 points in economy (plus taxes). However, you will still need to call Qantas to book if you do find flights.